Ferroelectric and high dielectric constant integrated circuit capacitors with three-dimensional orientation for high-density memories, and method of making the same

ABSTRACT

A three-dimensional (“3-D”) memory capacitor comprises a bottom electrode, a ferroelectric thin film, and a top electrode that conform to a 3-D surface of an insulator layer. The capacitance area is greater than the horizontal footprint area of the capacitor. Preferably, the footprint of the capacitor is less than 0.2 nm 2 , and the corresponding capacitance area is typically in a range of from 0.4 nm 2  to 1.0 nm 2  The ferroelectric thin film preferably has a thickness not exceeding 60 nm. A capacitor laminate including the bottom electrode, ferroelectric thin film, and the top electrode preferably has a thickness not exceeding 200 nm. A low-thermal-budget MOCVD method for depositing a ferroelectric thin film having a thickness in a range of from 30 nm to 90 nm includes an RTP treatment before depositing the top electrode and an RTP treatment after depositing the top electrode and etching the ferroelectric layer.

CROSS-REFERENCE TO RELATED APPLICATIONS

This Application is a divisional of U.S. patent application Ser. No.10/626,413 filed on Jul. 24, 2003, which is a continuation-in-partapplication under 37 CFR 1.53(b) of U.S. patent application Ser. No.10/302,441 filed Nov. 22, 2002, and U.S. patent application Ser. No.10/302,442 filed Nov. 22, 2002, and U.S. patent application Ser. No.09/998,469 filed Nov. 29, 2001, which are hereby incorporated byreference.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention pertains to the field of high-density memoriesand, particularly, memories that utilize ferroelectric capacitors.

2. Statement of the Problem

Ferroelectric memories are nonvolatile memories offering performance anddensification advantages over conventional nonvolatile memories, such aselectrically erasable programmable read only memories (EEPROM) anderasable programmable read only memories (EPROM). U.S. Pat. No.5,046,043 issued Sep. 3, 1991 to Miller et al. shows a 1T/1C memory cellhaving a lead zirconium titanate (PZT) ferroelectric capacitoralternatively stacked over a contact hole or within a conduit leading tothe transistor source/drain region. The configuration of the Miller etal. ferroelectric memory cells is similar to that of a conventionaldynamic random access memory (DRAM) cell. However, the operation andtiming are different, particularly in that the cell does not need to berefreshed as often because memory storage is relatively permanent. Arefresh operation is one in which the memory logic senses the state ofthe memory cells and writes the state of the memory that has been sensedback to the memory cells in an identical format to that which has beensensed.

Permanence or nonvolatility of memory storage results from the abilityof ferroelectric materials to polarize in the presence of an appliedelectric field, and to retain that polarization state once the field isremoved. Thus, a logical one or zero is represented by the polarizationstate of the ferroelectric material in the capacitor. Memory senseamplifiers and logic circuits are used to determine the polarizationstate for memory operations in a conventional manner for ferroelectricmemories.

U.S. Pat. No. 5,227,855 issued Jul. 13, 1993 to Hisayo S. Momose shows aone-transistor one-capacitor (1T/1C) memory cell where a PZTferroelectric capacitor resides in a contact hole contacting asource/drain region of the field effect transistor. The purpose ofplacing the capacitor in the contact hole is to make the memory cellflatter and facilitate the formation of metal wiring layers in thecontact holes. A discussion of the prior art in the Momose patent showsthe ferroelectric capacitor located above the transistor gate with awiring layer extending to the side of the gate region for contact withthe transistor source/drain region. The thin films in all of theseferroelectric capacitors have a horizontal orientation parallel to thatof the underlying substrate. The discussion below shows that designs toplace ferroelectric capacitors in transistor contact holes is, to acertain extent, wishful thinking because the contact holes must beexceptionally large.

In high-density memories, a significant problem with placing theferroelectric capacitor in the contact hole leading to the transistorsource-drain region is that the ferroelectric capacitor must becontained within limited surface area due to the small overall size ofthe device. Ferroelectric polarization depends primarily on crystalgrain surface area, which is typically measured in units ofmicrocoulombs per square centimeter. These grains are sometimes referredto as ferroelectric domains. While increasing the thickness of theferroelectric layer can increase polarization by increasing the numberof vertically stacked domains, increasing the thickness also reduces theapplied electric field at some of the domains. As a result, the appliedfield is greater for some domains and less for other domains. A reducedfield is less effective at switching domains, and the unequal switchingability in thicker films results in some domains being incompletelyswitched.

Ferroelectric films, if left in a polarized state, tend to retain theirpolarization state for periods of weeks, months, or years; however, inactual use, ferroelectric films retain their polarization states formuch shorter times because they are sensitive to disturb voltage pulses.Disturb voltage pulses are unidirectional voltage pulses that switch thepolarization state in only a portion of the ferroelectric domains.Current ferroelectric memory architecture requires ferroelectricmaterials to be exposed to disturb voltage pulses. Disturb voltagepulses have been shown to degrade remnant polarization in PZT capacitorshaving a 1.84×10⁻⁴ cm² surface area to fifty percent of original levelsafter 10⁷ cycles of 1.0V pulses 1 μs apart with 100 ns rise and falltimes. See Moore et al., “The Effect of Small Voltage Pulses on RetainedPolarization in Ferroelectric Capacitors” (undated). Thus, the combinedeffects of low polarization due to small capacitance area together withdisturb voltage pulsing requires ferroelectric memories to be refreshed.Even if the disturb pulses do not switch the ferroelectric, senseoperations are increasingly prone to errors because the retainedpolarization has a lower magnitude that is more difficult to readwithout switching the polarization state of the ferroelectric material.

One way to avoid the problems that are caused by small capacitance areais to provide a capacitor having a large surface area. PCT PublicationNo. WO 93/12542 published Jun. 24, 1993 to Araujo et al. shows a 1T/1Cmemory cell having a horizontally oriented, vertically stackedferroelectric capacitor with a much greater surface area than thetransistor component of the memory cell. The ferroelectric capacitorcovers a surface area off to the side of the transistor, and onlypartially overlaps the transistor. The overall surface area of thecapacitor is much greater than the contact hole leading to thetransistor active area. This semi-overlapping design uses a layeredsuperlattice material as the ferroelectric. The need for ferroelectriccapacitors having relatively large surface areas in high-densitymemories is apparent from the WO 93/12542 memory cell because theferroelectric capacitor occupies several times the surface area of thetransistor device even though layered superlattice materials have betterpolarizabilities than do comparable PZT films. A further reason forplacement of the ferroelectric capacitor off to the side of thetransistor is that the metals in the ferroelectric material mightotherwise be more prone to diffuse into the transistor active area wherethey interfere with the intended n and p dopants.

FIG. 1 shows a cross-sectional view of another typical conventionalnonvolatile ferroelectric memory 100 of the prior art. Ferroelectricmemory capacitor 128 includes bottom electrode 122, ferroelectric thinfilm 124, and top electrode 126, which are substantially parallel tounderlying semiconductor substrate 102. The effective capacitance areaof memory capacitor 128 is generally determined by the smallesthorizontal surface area of the active capacitor elements. In capacitor128, active capacitor elements bottom electrode 122, ferroelectric thinfilm 124, and top electrode 126 have substantially the same horizontalsurface area. To increase the polarizability of capacitor 128 of theprior art, it would be necessary to increase the horizontal surface areaof the active capacitor elements. This would increase the horizontalsurface area (“footprint”) of capacitor 128, thereby decreasing thedensity of memory 100.

The ever-increasing density of integrated circuits, however, requires acorresponding decrease in the horizontal surface area of memory cells,while maintaining good electronic properties, such as goodpolarizability and low coercive voltage. Thus, there remains a need toprovide a ferroelectric capacitor for high-density memories where thefootprint of the capacitor is reduced with a corresponding increase inmemory density.

BRIEF SUMMARY OF THE INVENTION

The present invention helps to overcome some of the problems outlinedabove by providing a ferroelectric capacitor device that occupies asmall horizontal surface area (“footprint”) while maintaining sufficientcapacitance area to provide good electronic properties. This advantageis obtained by forming the active elements of a ferroelectric memorycapacitor in a shape having substantial directional components that areperpendicular to the underlying substrate, as opposed to a planarorientation that is predominantly parallel to the underlying substrate.A capacitor dielectric thin film comprising ferroelectric material ispreferably fabricated using an MOCVD technique, which enables thedeposition of an ultra-thin film having a thickness not exceeding 80nanometers (nm) and good step-coverage conforming to a three-dimensional(“ 3-D”) shape of a memory capacitor.

In one aspect, a ferroelectric integrated circuit memory in accordancewith the invention comprises a 3-D capacitor laminate, the capacitorlaminate comprising a bottom electrode, a ferroelectric film, and a topelectrode, wherein the 3-D capacitor laminate comprises a 3-D shapehaving substantial directional components in three mutually orthogonalplanes. Preferably, the ferroelectric film has a thickness not exceeding80 nm, and more preferably, not exceeding 60 nm. Preferably, theferroelectric film comprises ferroelectric layered superlatticematerial. In some embodiments, the ferroelectric film comprisesstrontium bismuth tantalate or strontium bismuth tantalum niobate. Inanother aspect, a capacitor laminate has a thickness not exceeding 300nm, preferably not exceeding 200 nm.

In still another aspect, a capacitor laminate defines a capacitance areaand a capacitor-footprint area, and the capacitance area exceeds thecapacitor-footprint area. Typically, the capacitance area is at leasttwo times greater than the capacitor-footprint area. Preferably, thecapacitance area is at least three times greater than thecapacitor-footprint area, and more preferably, it is at least four timesgreater than the capacitor-footprint area. In some embodiments, thecapacitor-footprint area does not exceed 0.5 nm². In other embodiments,the capacitor-footprint area does not exceed 0.2 nm².

In another aspect, a ferroelectric integrated circuit memory inaccordance with the invention comprises a plurality of capacitorlaminates.

In another aspect, the bottom electrode, the ferroelectric film, and thetop electrode conform substantially to a 3-D shape.

Some embodiments further comprise a nonconductive hydrogen barrier layerdisposed above the capacitor laminate, the nonconductive hydrogenbarrier layer comprising strontium tantalate.

In embodiments in accordance with the invention, a capacitor laminatecan have virtually any 3-D shape that provides a substantially greatereffective capacitor surface area, or capacitance area, than itscapacitor-footprint area. For example, some embodiments arecharacterized by a trench-shaped capacitor laminate. Accordingly, theferroelectric integrated circuit memory preferably comprises aninsulator layer having an insulator top surface, and a trench locatedsubstantially in the insulator layer, the trench having a trench bottom,a trench sidewall, and a trench opening substantially coplanar with theinsulator top surface. A bottom electrode substantially conforms to thetrench bottom and the trench sidewall. A ferroelectric film is disposedabove the bottom electrode layer and conforms substantially to thebottom electrode. Atop electrode is disposed above the ferroelectricfilm and substantially conforms to the ferroelectric film. In oneaspect, the trench opening has a trench opening area and the toplaminate surface has a laminate area, the laminate area being greaterthan the trench opening area. Typically, the laminate area is more thantwo times greater than the trench opening area. Preferably, the trenchopening area does not exceed 0.5 nm², and more preferably it does notexceed 0.2 nm². In another aspect, a ferroelectric integrated circuitmemory in accordance with the invention comprises a plurality oftrenches and a plurality of corresponding capacitor laminates. Inpreferred embodiments, a distance between two adjacent trenches does notexceed 250 nm.

In some embodiments, a ferroelectric integrated circuit memory comprisesa capacitor laminate having a 3-D pillar shape. A correspondingintegrated circuit preferably comprises an insulator layer having apillar of insulating material, the pillar having a pillar top: surfaceand a pillar sidewall. A bottom electrode covers a portion of thepillar, the bottom electrode substantially conforming to the pillar topsurface and to a portion of the pillar sidewall. A ferroelectric film isdisposed above the bottom electrode layer, the ferroelectric filmsubstantially conforming to the bottom electrode. A top electrode isdisposed above the ferroelectric film, the top electrode substantiallyconforming to the ferroelectric film. Characteristically, the bottomelectrode, the ferroelectric film, and the top electrode are each partof a 3-D capacitor laminate, the 3-D capacitor laminate has a laminatethickness and a top laminate surface, and the pillar sidewall defines apillar height, and the laminate thickness is less than the pillarheight. In another aspect, the pillar top surface has a pillar top areaand the top laminate surface has a laminate area, the laminate areabeing greater than the pillar top area. Typically, the laminate area ismore than two times greater than the pillar top area. Typically, thepillar top area does not exceed 0.5 nm², and more preferably it does notexceed 0.2 nm². In still another aspect, a ferroelectric integratedcircuit memory comprises a plurality of pillars and a plurality ofcorresponding capacitor laminates. Typically, a distance between twoadjacent pillars does not exceed 250 nm.

A preferred method of forming a ferroelectric memory in an integratedcircuit substrate in accordance with the invention comprises providingan integrated circuit portion having a 3-D bottom electrode. The methodfurther comprises depositing a conformal ferroelectric thin film layerconforming to the bottom electrode layer using an MOCVD technique, andthen depositing a conformal top electrode layer conforming to theferroelectric thin film layer. Preferably, the integrated circuitsubstrate includes a switch and an insulator layer above the switch,wherein a portion of the insulator layer comprises a 3-D insulatorsurface, and the bottom electrode is formed conformal to said insulatorsurface. Typically, the method preferably further comprises processes ofremoving a portion of the top electrode layer, a portion of theferroelectric thin film layer, and a portion of the bottom electrodelayer to form a 3-D capacitor laminate including a top electrode, aferroelectric film, and a bottom electrode. Preferably, depositing aconformal ferroelectric thin film layer comprises depositing aferroelectric thin film layer having a thickness not exceeding 80 nm,and more preferably not exceeding 60 mL

Preferably, depositing a conformal ferroelectric thin film layer isconducted using a low-thermal-budget MOCVD technique. In one aspect,using an MOCVD technique typically comprises flowing a metal organicprecursor into an MOCVD reaction chamber containing the integratedcircuit substrate to form a coating on the conformal bottom electrodelayer, wherein the precursor contains metal atoms in effective amountsfor forming the ferroelectric thin film layer, and heating the substrateincluding the coating using rapid thermal processing at a temperature ina range of about from 500° C. to 900° C. for a cumulative heating timenot exceeding 30 minutes, and preferably less than five minutes.Typically, a method in accordance with the invention is furthercharacterized by not heating the substrate in a furnace. Typically,heating the substrate comprises conducting a pre-TE RTP-treatment of thesubstrate including the coating before depositing the top electrodelayer, and conducting a post-TE RTP-treatment after depositing the topelectrode layer. Typically, a method further comprises processes ofremoving a portion of the top electrode layer, a portion of theferroelectric thin film layer, and a portion of the bottom electrodelayer to form a 3-D capacitor laminate including a top electrode, aferroelectric film, and a bottom electrode before conducting the post-TERTP-treatment. In some embodiments, a post-TE RTP-treatment is conductedin a nonreactive gas. Preferably, the MOCVD ferroelectric thin film isformed of a layered superlattice material.

The invention also provides a ferroelectric integrated circuit memorycomprising: a 3-D capacitor laminate, the capacitor laminate comprisinga bottom electrode, a ferroelectric film comprising a layeredsuperlattice material, and a top electrode; wherein the 3-D capacitorlaminate comprises a 3-D shape having substantial directional componentsin three mutually orthogonal planes. Preferably, the layeredsuperlattice material comprises a material selected from the groupconsisting of strontium bismuth tantalate, strontium bismuth tantalumniobate, and bismuth lanthanum titanate.

The invention further provides a ferroelectric integrated circuit memorycomprising: a 3-dimensional (“3-D”) capacitor laminate, the capacitorlaminate comprising a bottom electrode, a ferroelectric film, and a topelectrode; wherein the 3-D capacitor laminate comprises a 3-D shapehaving substantial directional components in three mutually orthogonalplanes; and wherein the capacitor laminate has a thickness not exceeding300 nm. Preferably, the capacitor laminate has a thickness not exceeding200 nm. Preferably, the laminate defines a capacitance area and acapacitor-footprint area, and the capacitance area exceeds thecapacitor-footprint area. Preferably, the capacitance area is at leasttwo times greater than the capacitor-footprint area. More preferably,the capacitance area is at least three times greater than thecapacitor-footprint area. Most preferably, the capacitance area is atleast four times greater than the capacitor-footprint area. Preferably,the capacitor-footprint area does not exceed 0.5 nm². More preferably,the capacitor-footprint area does not exceed 0.2 nm². Preferably, theferroelectric film has a thickness not exceeding 80 nm. More preferably,the ferroelectric film has a thickness not exceeding 60 nm.

Numerous other features, objects and advantages of the invention willbecome apparent from the following description when read in conjunctionwith the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 depicts in schematic form a section of a ferroelectric memorycell of the prior art, in which the active elements of a memorycapacitor are substantially parallel to the underlying semiconductorsubstrate;

FIGS. 2 and 2A depict mutually orthogonal sectional views of aferroelectric memory cell in accordance with the invention, in whichactive elements of a ferroelectric memory capacitor have a 3-Dtrench-shape including directional components substantiallyperpendicular to the underlying semiconductor substrate;

FIG. 3 depicts in schematic form a top view of a horizontal section ofthe substrate shown in FIGS. 2, 2A;

FIG. 4 contains a process flow sheet of a method for fabricating anintegrated circuit having a 3-D ferroelectric memory capacitor inaccordance with the invention as depicted in FIGS. 2, 2A;

FIGS. 5 and 5A depict mutually orthogonal sectional views of anintermediate fabrication stage of a ferroelectric memory cell inaccordance with the invention on the substrate of FIGS. 2, 2A;

FIGS. 6 and 6A depict mutually orthogonal sectional views of thesubstrate of FIGS. 5, 5A in a further intermediate fabrication stage ofa ferroelectric memory cell in accordance with the invention;

FIGS. 7 and 7A depict mutually orthogonal sectional views of thesubstrate of FIGS. 6, 6A in a further intermediate fabrication stage ofa ferroelectric memory cell in accordance with the invention;

FIGS. 8 and 8A depict mutually orthogonal sectional views of thesubstrate of FIGS. 7, 7A in a further intermediate fabrication stage ofa ferroelectric memory cell in accordance with the invention;

FIGS. 9 and 9A depict mutually orthogonal sectional views of analternative embodiment of a ferroelectric memory cell in accordance withthe invention, in which active elements of a ferroelectric memorycapacitor have a 3-D pillar-shape including directional componentssubstantially perpendicular to the underlying semiconductor substrate;

FIGS. 10 and 10A depict mutually orthogonal sectional views of anintermediate fabrication stage of a ferroelectric memory cell inaccordance with the invention on the substrate of FIGS. 9, 9A;

FIGS. 11 and 11A depict mutually orthogonal sectional views of thesubstrate of FIGS. 10, 10A in a further intermediate fabrication stageof a ferroelectric memory cell in accordance with the invention; and

FIG. 12 contains a process flow sheet of a method for fabricating anintegrated circuit having a 3-D ferroelectric memory capacitor inaccordance with the invention as depicted in FIGS. 9, 9A.

DETAILED DESCRIPTION OF THE INVENTION

Embodiments in accordance with the invention are described herein withreference to FIGS. 2-11B. It should be understood that FIGS. 2, 2A, 3,and 5A through 11B, depicting integrated circuit devices, are not meantto be actual plan or cross-sectional views of any particular portion ofan actual integrated circuit device. In the actual devices, the layerswill not be as regular and the thickness may have different proportions.The various layers in actual devices often are curved and possessoverlapping edges. The figures instead show idealized representationswhich are employed to explain more clearly and fully the method of theinvention than would otherwise be possible. Also, the figures representonly one of innumerable variations of ferroelectric devices that couldbe fabricated using the method of the invention.

It also should be noted that the figures that are paired as a figureidentified with a number above another figure with the same numberfollowed by the letter “A” are mutually orthogonal cross sections of thesame integrated circuit wafer. That is, FIGS. 2 and 2A are mutuallyorthogonal cross-sectional views of the same wafer, FIGS. 5 and 5A aremutually orthogonal cross-sectional views of the same wafer, and so on.

Embodiments in accordance with the invention are described herein mainlywith reference to ferroelectric integrated circuit memories, and inparticular, to memory capacitors containing a conformal thin film offerroelectric layered superlattice material fabricated using an MOCVDtechnique. It is understood, however, that structures and methods inaccordance with the invention are useful for making and using memorycapacitors that include a nonferroelectric dielectric thin film insteadof a ferroelectric thin film, or that contain a ferroelectric thin filmcomprising a material that is not a layered superlattice material

General manufacturing processes for fabricating integrated circuitscontaining MOSFETs and ferroelectric capacitor elements are described inU.S. Pat. No. 5,466,629 issued Nov. 14, 1995 to Mihara et al., and U.S.Pat. No. 5,468,684 issued Nov. 21, 1995 to Yoshimori et al., which arehereby incorporated by reference as if fully disclosed herein. Generalfabrication methods have been described in other references also.

The preferred ferroelectric materials utilized in the invention compriselayered superlattice materials as described in U.S. Pat. No. 5,519,234issued May 21, 1996 to Paz de Araujo et al., which is herebyincorporated herein by reference. Strontium bismuth tantalate is anexample of a layered superlattice material. U.S. Pat. No. 5,434,102issued Jul. 18, 1995, to Watanabe et al., and U.S. Pat. No. 5,468,684issued Nov. 21, 1995, to Yoshimori et al., also both hereby incorporatedby reference as though fully disclosed herein, describe processes forintegrating these materials into practical integrated circuits. Thelayered superlattice materials may be summarized generally under theformula:A1_(w1) ^(+a1)A2_(w2) ^(+a2) . . . Aj_(wj) ^(+aj)S1_(x1) ^(+s1)S2 _(x2)^(+S2) . . . Sk_(xk) ^(+sk)B1_(y1) ^(+b1)B2_(y2) ^(+b2) . . . Bl_(yl)^(+bl)Q_(z) ^(−q)where A1, A2 . . . Aj represent A-site elements in the perovskite-likestructure, which may be elements such as strontium, calcium, barium,bismuth, lead, and others; S1, S2 . . . Sk represent superlatticegenerator elements, which usually is bismuth, but can also be materialssuch as yttrium, scandium, lanthanum, antimony, chromium, thallium, andother elements with a valence of +3; B1, B2 . . . B1 represent B-siteelements in the perovskite-like structure, which may be elements such astitanium, tantalum, hafnium, tungsten, niobium, zirconium, and otherelements; and Q represents an anion, which generally is oxygen but mayalso be other elements, such as fluorine, chlorine, and hybrids of theseelements, such as the oxyfluorides, the oxychlorides, etc. Thesuperscripts in formula (1) indicate the valences of the respectiveelements; for example, if Q is oxygen, then q=2. The subscripts indicatethe number of moles of the material in a mole of the compound, or interms of the unit cell, the number of atoms of the element, on theaverage, in the unit cell. The subscripts can be integer or fractional.That is, formula (1) includes the cases where the unit cell may varyuniformly throughout the material; for example, inSrBi₂(Ta_(0.75)Nb_(0.25))₂O₉, 75% of the B-sites are occupied bytantalum atoms, and 25% of the B-sites are occupied by niobium atoms. Ifthere is only one A-site element in the compound, then it is representedby the “A1” element and w2 . . . wj all equal zero. If there is only oneB-site element in the compound, then it is represented by the “B1”element, and y2 . . . yl all equal zero, and similarly for thesuperlattice generator elements. The usual case is that there is oneA-site element, one superlattice generator element, and one or twoB-site elements, although formula (1) is written in the more generalform since the invention is intended to include cases where either ofthe sites and the superlattice generator can have multiple elements. Thevalue of z is found from the equation:(a1w1+a2w2 . . . +ajwj)+(s1x1+s2x2 . . . +skxk)+(b1y1+b2y2 . . .+blyl)=qz.  (2)

Formula (1) includes all three of the Smolenskii type compoundsdiscussed in U.S. Pat. No. 5,519,234 referenced above. The layeredsuperlattice materials do not include every material that can be fitinto Formula (1), but only those which form crystaline structures withdistinct alternating layers.

U.S. Pat. No. 5,803,961 issued Sep. 8, 1998 to Azuma et al., which ishereby incorporated herein by reference as though fully disclosedherein, discloses that mixed layered superlattice materials, such asstrontium bismuth tantalum niobate, have improved properties inferroelectric applications. The mixed layered superlattice materials arecharacterized by nonstoichiometric amounts of A-site and B-siteelements. For example, a preferred precursor used in accordance with theinvention comprises metal organic precursor compounds having metals inrelative molar proportions corresponding to the stoichiometricallyunbalanced formula Sr_(0.8)Bi₂(Ta_(0.7)Nb_(0.3))₂O_(8.8).

Currently, ferroelectric layered superlattice materials, like the metaloxides SrBi₂Ta₂O₉ (SBT), SrBi₂(Ta_(1-x)Nb_(x))₂O₉ (SBTN), where 0≦x≦1,and particularlySr_(a)Bi_(b)(Ta_(1−x)Nb_(x))_(c)O_([9+(a−1)+(b−2)(1.5)+(c−2)(2.5)]),where 0.8≦a≦1, 2≦b≦2.2, 0≦x≦0.3 and 1.9≦c≦2.1 (SBTN), are being used andare under further development for use as capacitor dielectric innonvolatile memory applications, such as in FeRAMs and nondestructibleread-out ferroelectric FETs. Polycrystalline thin films of these layeredsuperlattice materials, as well as other layered superlattice materialsrepresented by Formula (1), may be fabricated and used in accordancewith the invention. Other layered superlattice materials that areparticularly useful in the invention include bismuth lanthanum titanate,sometimes referred to as BLT.

The word “substrate” can mean the underlying semiconductor material 204on which the integrated circuit is formed, as well as any object onwhich a thin film layer is deposited. In this disclosure, “substrate”shall generally mean the entire workpiece as it exists at a particularphase of fabrication and on which a particular fabrication process isbeing conducted.

The long dimensions of integrated circuit substrate 203, 503 andsemiconductor material 204, 504 in FIGS. 2, 2A and FIGS. 9A, 9B,respectively, and in related figures, are considered to be a“horizontal” plane herein, and directions perpendicular to this planeare considered to be “vertical”. Terms of orientation herein, such as“above”, “top”, “upper”, “below”, “bottom”, and “lower”, mean relativeto semiconductor material 204, 504. That is, if a second element is“above” a first element, it means it is farther from semiconductormaterial 204, 504; and if it is “below” another element, then it iscloser to semiconductor material 204, 504 than the other element. Termssuch as “above”, “below”, and “on” do not, by themselves, signify directcontact, although a layer that is above, below, or on another layer canalso be in direct contact with the layer. However, terms such as“directly on” or “onto” do signify direct contact of one layer with anunderlying layer. It is understood that thin films of layeredsuperlattice material fabricated in accordance with the invention havevarious shapes and conform to various topographies and features of anintegrated circuit substrate. Accordingly, thin films of layeredsuperlattice material in accordance with the invention are formed onplanar substrates, in trenches and vias, on vertical sidewalls, and inother various non-horizontal and three-dimensional shapes. As depictedin FIGS. 2, 2A and FIGS. 9, 9B, a layer of memory cells comprisingswitches and capacitors is formed on semiconductor material 204, 504 ofan integrated circuit substrate 203, 503. It is understood thatembodiments in accordance with the invention also provide a plurality oflayers of memory cells formed sequentially one on top of the other on asingle integrated circuit substrate.

The terms “three mutually orthogonal planes”, “three orthogonaldirections”, and similar terms are used synonymously to describe a shapeof an element or a combination of elements in structures in accordancewith the invention. The terms signify that a shape has directionalcomponents in three mutually orthogonal planes, for example, in the x,y, and z planes of a Cartesian coordinate system.

The term “capacitance area” and similar terms refer to the effectivesurface area of a capacitor that determines capacitance. Typically, thecapacitance area of a capacitor is determined by the smallest surfacearea of the top electrode, the capacitor dielectric, and the bottomelectrode.

The term “conformal”, when applied to an integrated circuit element,means that the element follows the contour of the underlying layer.Preferably, the conformal layers in this disclosure are also smooth,continuous, and uniform.

The term “thin film” is used herein as it is used in the integratedcircuit art. Generally, it means a film of less than a micron inthickness. The thin films disclosed herein are usually less than 500nanometers (nm) in thickness, and more typically in a range of aboutfrom 5 nm to 200 nm. For example, a thin film of layered superlatticematerial fabricated in an integrated circuit in accordance with theinvention typically has a final thickness in a range of from 25 nm to150 nm. The “thickness” of a 3-D electrode, a 3-D ferroelectric thinfilm, or a 3-D capacitor laminate in accordance with the inventionrefers to the thickness as would be measured perpendicular to a tangentline at the surface of the thin film at any given point. These thinfilms of the integrated circuit art should not be confused with thelayered capacitors of the macroscopic capacitor art which are formed bya wholly different process that is incompatible with the integratedcircuit art. The term “MOCVD ferroelectric film” and similar terms referto a ferroelectric thin film fabricated using a MOCVD technique,preferably using a low-thermal-budget MOCVD technique as disclosed inU.S. patent application Ser. No. 10/302,441 filed Nov. 22, 2002, whichis incorporated by reference.

The term “stoichiometric” herein may be applied to both a solid film ofa material, such as a layered superlattice material, or to the precursorfor forming a material. When it is applied to a solid thin film, itrefers to a formula which shows the actual relative amounts of eachelement in a final solid thin film. When applied to a precursor, itindicates the molar proportion of metals in the precursor. A “balanced”stoichiometric formula is one in which there is just enough of eachelement to form a complete crystal structure of the material with allsites of the crystal lattice occupied, though in actual practice therealways will be some defects in the crystal at room temperature. Forexample, both SrBi₂(TaNb)O₉ and SrBi₂(Ta_(1.5)Nb_(0.5))O₉ are balancedstoichiometric formulae. In contrast, a precursor for strontium bismuthtantalum niobate in which the molar proportions of strontium, bismuth,tantalum, and niobium are 0.9, 2.18, 1.5, and 0.5, respectively, isrepresented herein by the unbalanced “stoichiometric” formulaSr_(0.9)Bi_(2.18)(Ta_(1.5)Nb_(0.5))O₉, since it contains excess bismuthand deficient strontium relative to the B-site elements tantalum andniobium. It is common in the art to write an unbalanced stoichiometricformula of a metal oxide in which the subscript of the oxygen symbol isnot corrected to balance completely the subscript values of the metals.

The word “precursor” used herein can mean a solution containing onemetal organic solute that is mixed with other precursors to formintermediate precursors or final precursors, or it may refer to a finalliquid precursor solution or gas mixture, that is, the precursor to beapplied to a particular surface during fabrication. The precursor asapplied to the substrate is usually referred to as the “finalprecursor”, “precursor mixture”, or simply “precursor”. In any case, themeaning is clear from the context.

A “precursor compound” in this disclosure refers to a metal organiccompound containing at least one metal that is included in a desiredlayered superlattice material of the ferroelectric thin film formed inaccordance with the invention. The metal organic precursor compoundsdisclosed herein are useful because they can be easily dissolved inorganic liquid precursor solutions, which can be stored until used. In aliquid-source misted chemical deposition (“LSMCD”) method in accordancewith the invention, one or more liquid precursor solutions are atomizedto form a mist that contains precursor compounds suitable for formationof a desired conformal thin film. See, for example, U.S. Pat. No.6,326,315 B1 issued Dec. 4, 2001 to Uchiyama et al., and U.S. Pat. No.6,258,733 B1 issued Jul. 10, 2001 to Solayappan et al., which are herebyincorporated by reference. In embodiments in accordance with theinvention utilizing an MOCVD technique to deposit a coating with desiredstoichiometry on a substrate, typically one or more liquid precursorstreams are vaporized, and then one or more gaseous precursor compoundsflow into a CVD reaction chamber, in which a solid coating containingdesired metal compounds forms on a wafer substrate. See, for example,U.S. Pat. No. 6,110,531 issued Aug. 29, 2000 to Paz de Araujo et al.,which is hereby incorporated by reference. The composition of aprecursor solution may be described in two ways. The actual dissolvedmetal organic precursor compounds (solutes) and solvents andconcentrations may be specified; or, for the sake of clarity, thestoichiometric formula representing the composition of the final oxidecompound to be formed with the precursor may be specified. Similarly, aprecursor compound may be described using its name or stoichiometricformula, or it may simply be identified by the metal atoms it contains.

Metal organic precursor compounds and liquid precursor solutions used inaccordance with the invention can be manufactured reliably. Theircomposition can be easily controlled and varied, if necessary. They canbe safely stored for long periods, up to six months. They are relativelynontoxic and nonvolatile, compared with many precursors of the priorart.

In one aspect, a method having a low thermal budget in accordance withthe invention generally minimizes the cumulative heating time that anintegrated circuit substrate is heated above 550° C. especially, itminimizes the thermal budget of operations conducted above 700° C. Theterms “cumulative heating time”, “total heating time”, and related termsin the specification designate the time during fabrication steps that anintegrated circuit substrate is heated at a temperature of 500° C. orgreater after an initial precursor coating is deposited on thesubstrate. During fabrication of an integrated circuit memory containinga capacitor comprising metal oxide dielectric material, in particular,ferroelectric layered superlattice material, the cumulative heating timerefers particularly to the total duration of substrate heating above500° C. from the point of starting to deposit an initial precursorcoating on the substrate to the point of forming metallization andwiring layers on the completed memory cell. In the prior art, when asubstrate including a ferroelectric coating was heated by RTP andfurnace at a temperature of 650° C. for 30 minutes before forming a topelectrode, and thereafter heated again in a furnace at 700° C. for 60minutes after formation of a top electrode, then the cumulative heatingtime was 90 minutes. In contrast, representative exemplary cumulativeheating times in low-thermal-budget MOCVD methods in accordance with theinvention are about two to three minutes or less.

The term “thermal budget” is also used herein in reference to a productof (elevated processing temperature) multiplied by (time at elevatedprocessing temperature). It has been observed that damage to anintegrated circuit resulting from heating at a given temperaturedecreases by reducing the duration of heating at that temperature.Further, it has been observed that damage to the integrated circuitfurther decreases by utilizing RTP heating. Damage from heating anintegrated circuit also decreases by heating at an increased temperaturefor a shorter amount of time. For example, generally less thermal damageoccurs by heating at 800° C. for 5 seconds, than by heating at 700° C.for 10 minutes. Therefore, in selecting operating conditions in methodsin accordance with the invention, a reduced heating time at a highertemperature is preferable to a longer heating time at a lowertemperature. Heating of an integrated circuit substrate to achieve goodcrystallization of layered superlattice materials (or other metal oxide)and to minimize thermal damage to the integrated circuit is influencedby a number of variables, including, but not limited to: heatingtemperature; total heating time at elevated temperature (e.g., 800° C.);thin film thickness; presence of oxygen; and relative location ofdiffusion barrier layers. For example, a thin film of layeredsuperlattice material having a thickness less than 100 nanometers (nm)generally requires a lower thermal budget to achieve good electronicproperties than a thicker film. In the field of reaction engineering, itis known that the reaction rate is generally proportional totemperature; that is, the reaction rate increases with temperature.Nevertheless, the proportional relationship of reaction rate totemperature is usually not linear. In the art, it is generally held thatreaction rate approximately doubles when temperature increases 10° C.Thus, by increasing the temperature of a chemical reaction process by30° C., for example, the time required for reaction is reduced to afraction of the time required without temperature increase. Efforts inthe prior-art to reduce thermal damage to integrated circuit memorycapacitors typically aimed to minimize the temperature levels at which amemory circuit was heated. In contrast, methods in accordance with thepresent invention are designed to minimize the thermal budget of aprocess, that is, the product of heating time and heating temperature.Because the relation between reaction temperature and reaction rate isnot linear, the heating time, and thereby the thermal budget of aprocess, are reduced by a relatively large amount through a relativelysmall increase in heating temperature. As a result, certain embodimentsin accordance with the invention conduct heating of an integratedcircuit memory substrate at temperatures higher than reported in theprior art, but during a much-reduced heating time.

The term “strontium tantalate” (or “strontium tantalum oxide”) hereinmeans any one or several of the oxide compounds comprising strontium andtantalum. Strontium tantalate in accordance with the invention isrepresented herein by the generalized stoichiometric formula SrTaO_(x),which represents strontium tantalate compounds including, but notlimited to, SrTa₂O₆ and Sr₂Ta₂O₇′

The terms “region” and “area” as used herein generally have their usualmeaning; that is, “area” generally designates a two-dimensional surface,whereas a “region” is generally three-dimensional. For example, a“non-memory area” of a layer or a substrate in this specificationgenerally corresponds to a “non-memory region” of an integrated circuitlocated below or above a non-memory area

The terms “dielectric thin film”, “capacitor dielectric”, and similarterms referring to a thin film of dielectric material between electrodesin a capacitor are used broadly to include not only the purelyinsulating dielectric materials, but also ferroelectric materials thatare both dielectric and ferroelectric, such as certain ABO₃-type oxidesand, in particular, ferroelectric layered superlattice materials.

The term “continuous” and similar terms used to describe a plate-lineelectrode or a diffusion barrier layer means substantially unbroken oruninterrupted.

Integrated circuit memory capacitors often include one or more layers inaddition to a top electrode, a capacitor ferroelectric or dielectricthin film, and bottom electrode. Such additional layers have variousnames, such as “buffer layer”, “adhesive layer”, “capping layer”, andothers. As disclosed variously in the art, such an additional layer maybe disposed between a ferroelectric or dielectric thin film and anadjacent electrode, or it may be disposed adjacent to an outside surfaceof an electrode. Also, such additional layers may be referred to as partof the ferroelectric or dielectric thin film, or as part of anelectrode. Therefore, in this specification, it is understood that a topelectrode, a ferroelectric or dielectric thin film, or a bottomelectrode in accordance with the invention may include an additionallayer as known in the art, without specific reference to such anadditional layer. Similarly, a method in accordance with the inventionmay further include formation of such an additional layer.

FIGS. 2, 2A depict mutually orthogonal cross-sectional views of anexemplary nonvolatile ferroelectric memory of integrated circuit 200 inaccordance with the invention. FIG. 2 shows a cross-section 201 takenalong the bit line 202 of integrated circuit 200. Integrated circuitmemory 200 includes silicon semiconductor material 204, field oxideregions 206, and switches 208. A switch 208 is typically a metal-oxidesemiconductor field-effect transistor (“MOSFET”), formed usingtechniques known in the art. A MOSFET switch 208 includes source/drainregions 210, 212, a channel region 214, and a gate 216, typicallycomprising a gate buffer layer, gate insulating layer, and gateelectrode. Integrated circuit memory 200 further includes a firstinsulator layer 218, typically called an interlayer dielectric layer(“ILD”), disposed on substrate 203, and covering semiconductor material204, oxide regions 206, and switches 208. First insulator layer 218typically comprises nondoped silicate glass (“NSG”) or a doped glass,such as BPSG (boron-doped phospho-silicate glass) and is typicallyformed using a CVD technique as known in the art. In other embodimentsin accordance with the invention, integrated circuit material 204comprises silicon germanium, gallium arsenide or other semiconductor, oran insulator such as magnesium oxide (MgO). Substrate 203 furtherincludes vias 220, 221 in which conductive capacitor plugs 222 andconductive bit-line plug 223, respectively, are disposed. Electricallyconductive plugs 222, 223 typically are formed by filling vias 220, 221with electrically conductive material and planarizing the surface ofsubstrate 203 so that the tops of plugs 222, 223 are approximatelycoplanar with first insulator layer 218, as depicted in FIG. 2. Plugs222, 223 are formed so that the bottom of each plug is in electricalcontact with switch 208. Preferably, conductive plugs 222, 223 comprisetungsten, which is deposited using techniques known in the art. In morepreferred embodiments, plugs 222, 223 are formed by depositing a layerof titanium having a thickness in a range of about from 5 nm to 30 nm invias 220, 221, followed by depositing a layer of titanium nitride havinga thickness in a range of about from 5 nm to 30 nm on the titanium,followed by deposition of tungsten.

Electrically conductive diffusion barrier material is deposited andpatterned on ILD 218 to form diffusion barriers 226, 227 in electricalcontact with plugs 222, 223, respectively. Diffusion barriers 226, 227are made of, for example, titanium nitride, and typically have athickness of 10 nm to 20 nm. Diffusion barrier layers, such as titaniumnitride, inhibit the diffusion of chemical species, particularly oxygen,between the underlying and overlying layers of integrated circuit memory200.

A second interlayer dielectric layer (ILD) 230 made of NSG (nondopedsilicate glass) is disposed on ILD 218 to cover ILD 218 and diffusionbarriers 226, 227. A doped silicate glass, such as FSG (fluorosilicateglass), PSG (phospho-silicate glass) film, or a BPSG (boronphospho-silicate glass) film could also be used in layer 230. ILD 230has a top surface 231. ILD 230 is patterned and etched to form trenches234.

In accordance with the invention, each trench 234 is lined with a 3-Dcapacitor laminate 240. A capacitor laminate 240 comprises a bottomelectrode 242, a ferroelectric thin film 244, and a top electrode 246.Trench 234 is three-dimensional; that is, the shape of trench 234 hassubstantial vertical components, or substantial directional componentssubstantially perpendicular to the horizontal plane of semiconductorsubstrate 204. As a result, capacitor laminate 240, which conformssubstantially to the shape of trench 234, also has a 3-D shape. Inpreferred embodiments, top electrode 246 is a top plate-line electrodethat extends substantially perpendicular to bit line 202 of FIG. 2.Capacitor laminate 240 in each trench 234 functions as a ferroelectricmemory capacitor 250 in integrated circuit 200. FIG. 2A depicts across-section 252 taken along a top plate-line electrode 246 ofintegrated circuit 200. Top plate-line electrode 246 is not planar,rather, it is a plate line in the sense that it extends continuouslybetween a plurality of memory capacitors 250 and provides continuouselectrical connection between the capacitors and a conductive plate-lineconnector plug 254. As depicted in FIG. 2, capacitor laminate 240 is notpresent on a non-capacitor area 256 of top surface 231 of ILD 230between adjacent capacitors 250 along bit line 202. Similarly, asdepicted in FIG. 2A, bottom electrode 244 is not present onnon-capacitor area 258 between adjacent capacitors 250 along topplate-line electrode 246. As depicted in FIGS. 2, 2A, an overlap portion260 of laminate 240 of each capacitor 250 typically slightly overlapstop surface 231 of ILD 230. The footprint, or horizontal surface area,of a capacitor 250 is determined essentially by the horizontal area oftrench 234 and the area of overlap portion 260. The capacitance area ofcapacitor 250, however, is represented approximately by the surface areaof the bottom and sidewall of trench 234 plus the area of overlapportion 260. A trench 234 is typically patterned to have a squarerectangular shape. In a square trench having a depth equal to the lengthof one of its sides, the surface area of its sidewall (all four squaresides) is four times greater than the surface area of its bottom (or ofits top). As a result, a capacitor 250 in accordance with the inventionhaving a footprint only one-fourth the horizontal surface area of aconventional horizontally-oriented capacitor of the prior art providesapproximately the same capacitance area. Similar relative proportionsobtain when trenches have circular shapes. A capacitor 250 in accordancewith the invention typically comprises a bottom electrode having athickness of about 50 nm, a ferroelectric thin film having a thicknessof about 50 nm to 60 nin, and a top electrode having a thickness ofabout 50 nm. Thus, a corresponding capacitor laminate 240 has athickness of about 150 nm to 170 nm. A corresponding cube-shaped trench234 in accordance with the invention has length, width, and depthdimensions of approximately 350 nm to 400 nm, that is, about 0.35 nm to0.40 nm. A capacitor 250 in accordance with the invention typically hasa footprint of approximately 0.2 nm². In contrast, a conventional memorycapacitor of the prior art, as depicted in FIG. 1, typically has afootprint of about 0.8 nm² or more.

The bottom and top electrodes of ferroelectric capacitors conventionallycontain platinum. It is preferable that the bottom electrode contains anon-oxidized precious metal such as platinum, palladium, silver, andgold. In addition to a precious metal, metal such as aluminum, aluminumalloy, aluminum silicon, aluminum nickel, nickel alloy, copper alloy,and aluminum copper may be used for electrodes of a ferroelectricmemory. Adhesive layers (not shown), such as titanium, enhance theadhesion of the electrodes to adjacent underlying or overlying layers ofthe circuits.

A third interlayer dielectric layer (ILD) 262 made of NSG (nondopedsilicate glass) is disposed on ILD 218 and top plate-line electrode 246,thereby covering ferroelectric 3-D memory capacitors 250. A dopedsilicate glass, such as FSG (fluorosilicate glass), PSG(phospho-silicate glass) film, or a BPSG (boron phospho-silicate glass)film may also be used in layer 262.

Hydrogen barrier layer 264 is disposed on ILD 262 to cover the surfacearea above ferroelectric thin film 244. The composition, fabrication,and etching of hydrogen barriers are known in the art. See, for example,U.S. Pat. No. 6,225,656 B1 issued May 1, 2001 to Cuchiaro et al., andU.S. Pat. No. 6,180,971 issued Jan. 30, 2001 to Maejima, which arehereby incorporated by reference. Preferably, hydrogen barrier layer 264comprises strontium tantalum oxide, as disclosed in co-owned andco-pending U.S. patent application Ser. No. 09/998,469 filed Nov. 29,2001. Typically, hydrogen barrier layer 264 is not present overnon-memory areas of the integrated circuit where there is noferroelectric thin film 244 needing protection against reactivehydrogen.

A fourth interlayer dielectric layer (ILD) 268 made of NSG (nondopedsilicate glass) is disposed on ILD 262 and diffusion barrier layer 264.A doped silicate glass, such as FSG (fluorosilicate glass), PSG(phospho-silicate glass) film, or a BPSG (boron phospho-silicate glass)film could also be used in layer 268. As depicted in FIG. 2,electrically conductive bit-line connector plug 270 connects bit line202 to switch 208 through conductive barrier 227 and bit-line plug 223.As depicted in FIG. 2A, electrically conductive plate-line connectorplug 254 connects wiring layer 272 to top plate-line electrode 246.

FIG. 3 depicts in schematic form a top view 280 of a section ofintegrated circuit substrate wafer 203 taken approximately through lines3 of FIGS. 2 and 2A. In section 280, memory regions 265, indicated bydashed rectangles, comprise memory capacitors 250 and MOSFET switches208 (not shown in FIG. 3). Although memory regions 265 are representedin FIG. 3 as having a rectangular shape, it is clear that memory regions265 in actual integrated circuits have different shapes depending on theparticular shapes, locations, and dimensions of capacitors 250 andswitches 208. Hydrogen barrier layer 264, depicted in FIGS. 2, 2A,typically covers memory region 265. Non-memory regions of substrate 203comprise non-memory regions 282 outside memory regions 265, asrepresented in FIG. 3. As indicated in FIGS. 2 and 3, a memory region265 typically comprises at least a portion of conductive bit-lineconnector plugs 223, 270, which provide electrical contact between aswitch 208 of a memory cell and a bit-line 202 of an integrated circuit.In preferred embodiments in accordance with the invention, as depictedin FIGS. 2A and 3, conductive plate-line connector plug 254 is disposedremotely from capacitors 250. It is a feature of certain preferredembodiments in accordance with the invention that a nonconductive burieddiffusion barrier (not depicted) is disposed throughout an extendedarea, typically substantially the entire area of an integrated circuit,as disclosed in U.S. patent application Ser. No. 10/302,442 filed Nov.22, 2002. In other words, buried diffusion barrier 226 is extended so itis disposed over the extended surface area of FIG. 3 and underliessubstantially completely all of the integrated circuit elements depictedin FIG. 3. Capacitors 250 are represented by rectangles in FIG. 3. Therectangles 250 also correspond to the areas of capacitor laminates 240of FIGS. 2, 2A, and therefore also represent the footprint offerroelectric memory capacitors 250. As depicted in FIG. 3, capacitorlaminate 240 is generally not present in non-capacitor areas 256 alongbit lines 202. Bottom electrode material is not present in non-capacitorareas 258 along top plate-line 246.

The diagram of FIG. 4 is a process flow sheet of a method 400 inaccordance with the invention for making a preferred embodiment of aferroelectric memory in accordance with the invention. This figure willbe discussed in conjunction with FIGS. 5 and 5A, 6 and 6A, 7 and 7A, and8 and 8A. In each case, the two figures are mutually orthogonal views ofthe same integrated circuit portion. That is, FIGS. 5 and 5A aremutually orthogonal views of the same integrated circuit portion, FIGS.6 and 6A are mutually orthogonal views of the same integrated circuitportion, and so on. Although method 400 of FIG. 4 is discussed hereinwith reference to FIGS. 2 and 5-8A, representing a ferroelectricintegrated circuit memory in successive stages of fabrication, it isclear that the method of FIG. 4 and numerous embodiments of a method inaccordance with the invention are useful generally for fabricating a 3-Dferroelectric memory capacitor.

In processes 404, a substrate 203 is provided containing siliconsemiconductor material 204, field oxide regions 206, switches 208, firstILD 218, and conductive plugs 222, 223, as described above withreference to FIG. 2 and as depicted in FIGS. 5, 5A. First insulatorlayer 218 typically comprises nondoped silicate glass (“NSG”) or a dopedglass, such as BPSG (boron-doped phospho-silicate glass), and istypically formed by reacting a precursor using a CVD technique as knownin the art. In other embodiments in accordance with the invention,integrated circuit substrate 203 comprises gallium arsenide or othersemiconductor, or an insulator such as magnesium oxide (MgO).

In processes 406, a conductive diffusion barrier layer is deposited andthen patterned and etched to form conductive diffusion barriers 226,227. An electrically conductive oxygen-diffusion barrier layer isdeposited on substrate 203 to cover first insulator layer 218 andconductive plugs 222, 223. In preferred embodiments, the electricallyconductive oxygen-diffusion barrier layer comprises a multilayerstructure comprising an iridium oxide sublayer, which is on an iridiumsublayer, which is on a titanium aluminum nitride sublayer, asrepresented by IrO_(x)/Ir/TiAlN. A preferred barrier stack is fabricatedby first sputtering a sublayer of titanium aluminum nitride having athickness of about 50 nm onto first ILD 218 and conductive plugs 222,223, then sputtering about 100 nm iridium metal onto the nitridesublayer, and then sputtering about 100 nm of iridium oxide onto theiridium sublayer. Thereafter, the conductive barrier layer is patternedand etched to remove conductive barrier material from ILD 218, exceptfor areas above conductive plugs 222, 223 and areas correspondingapproximately to the footprints of capacitors 250.

In processes 408, second ILD 230 is formed on substrate 203, typicallyby depositing approximately 500 nm NSG or doped silicate glass byreacting TEOS or other known precursor using a PECVD technique known inthe art.

In processes 410, portions of second ILD 230 are removed usingpatterning and etching techniques known in the art to form trenches 234.Trenches 234 each have a sidewall 284 and a trench bottom 286 defined atleast partially by conductive barrier 226. A trench bottom 286 may alsocomprise insulator material associated with ILD 218 or ILD 230.Typically, patterning of ILD 230 is done in a rectangular or squareshape so that trenches 234 have shapes corresponding substantially tosquares or rectangles. It is understood, however, that trenches 234 maybe patterned and etched to have virtually any shape, for example, acylindrical shape. Furthermore, standard etching techniques usually formtrenches having sidewalls that are not perfectly parallel to thedirection of etching, that is, that are not perfectly perpendicular tothe horizontal plane of semiconductor substrate 204. As a result, thetop region 288 of a trench 234 is typically wider than a correspondingtrench bottom 286. Nevertheless, a sidewall 284 and capacitor layersconforming to sidewall 284 have substantial directional components inthe vertical direction, as well as in the horizontal planes at thebottom 286 and top 288, and are therefore three-dimensional

In processes 412, a conformal bottom electrode layer 242 a is depositedin trenches 234 and on second ILD 230, as depicted in FIG. 6.Preferably, the conformal bottom electrode layer has a thickness ofabout 50 nm and comprises platinum. Typically, a bottom electrode layeris formed by sputtering a platinum target using techniques known in theart. Preferably, the electrode is formed by RF sputtering of a platinumsingle layer, but it also may be formed by DC sputtering, ion beamsputtering, vacuum deposition, or other appropriate conventionaldeposition process. The bottom and top electrodes of memory capacitorsin accordance with the invention preferably contain platinum.Nevertheless, in certain embodiments, a bottom electrode comprisesanother non-oxidized precious metal, such as palladium, silver, andgold. In addition to the precious metals, a metal such as aluminum,aluminum alloy, aluminum silicon, aluminum nickel, nickel alloy, copperalloy, and aluminum copper may be used to form electrodes of a memorycapacitor in accordance with the invention.

In processes 414, portions of the bottom electrode layer 242 a areremoved from ILD 230, but not from the trenches. In preferredembodiments, a TEOS hardmask having a thickness of about 300 nm isdeposited on the bottom electrode layer 242 a using a CVD techniqueknown in the art. The TEOS hardmask then is patterned usingphotolithography techniques known in the art, for example, by depositinga resist, then exposing and developing the resist. A stack etch is thenconducted, typically using RIE, to etch portions of the bottom electrodelayer 242 a from non-capacitor areas 258, as depicted in FIG. 6A. Thehardmask then is removed from the top surface of the remaining bottomelectrode layer 242 a using techniques known in the art.

In processes 416, a conformal ferroelectric thin film layer 244 a oflayered superlattice material, or a thin film containing another type ofcapacitor dielectric, is deposited on the bottom electrode layer 242 aand on non-capacitor areas 258 of second ILD 230 in accordance with theinvention, as depicted in FIGS. 7, 7A. Prior to processes 416 ofpreferred embodiments, chemical precursors of the desired layeredsuperlattice material are prepared. Usually, precursor solutions areprepared from commercially available solutions containing the chemicalprecursor compounds. If necessary, the concentrations of the variousprecursors supplied in the commercial solutions are adjusted toaccommodate particular manufacturing or operating conditions. Morepreferred embodiments in accordance with the invention utilize a finalliquid precursor solution containing relative molar proportions of theelements strontium, bismuth, tantalum, and niobium correspondingapproximately to SrBi₂Ta₂O₉ (SBT), SrBi₂(Ta_(1-x)Nb_(x))₂O₉ (SBTN),where 0≦x≦1, and particularlySr_(a)Bi_(b)(Ta_(1−x)Nb_(x))_(c)O_([9+(a−1)+(b−2)(1.5)+(c−2)(2.5)]),where 0.8≦a≦1, 2≦b≦2.2, 0≦x≦0.3, and 1.9≦c≦2.1. Liquid-source metalorganic chemical deposition (“LSMCD”) and CVD methods for preparing thinfilms of ferroelectric layered superlattice material have been describedin the prior art, including U.S. Pat. No. 6,326,315 issued Dec. 4, 2001to Uchiyama et al.; U.S. Pat. No. 6,245,580 issued Jun. 12, 2001 toSolayappan et al.; and U.S. Pat. No. 6,110,531 issued Aug. 29, 2000 toPaz de Araujo et al.; which are hereby incorporated by reference. Inpreferred embodiments, dielectric layer 244 a comprising ferroelectriclayered superlattice material has a thickness in a range of about from25 nm to 300 nm, preferably about 50 nm to 60 nm. Preferably, processes416 include a pre-top-electrode RTP treatment (“pre-TE RTP”) inaccordance with a preferred low-thermal-budget MOCVD method for forminglayered superlattice material, as described in co-owned and co-pendingU.S. patent application Ser. No. 10/302,441 filed Nov. 22, 2002, havingthe title “Low Thermal Budget Fabrication of Ferroelectric Memory UsingRTP”, which is incorporated by reference. For example, after formationof a coating on the substrate in a CVD reaction chamber, a suitablepre-TE RTP treatment in accordance with the invention includes RTP at650° C. for 30 seconds in O₂ gas, with a ramping rate of 100° C. persecond to form a ferroelectric film

In processes 418, a top plate-line electrode layer 246 a is deposited onferroelectric layer 244 a, as depicted in FIGS. 7, 7A. Typically, topplate-line electrode layer 246 a is formed by depositing about 50 nm ofplatinum using a sputtering technique as known in the art. Preferably,the electrode is formed by RF sputtering of a platinum single layer, butit also may be formed by DC sputtering, ion beam sputtering, vacuumdeposition, or other appropriate conventional deposition process.

In processes 420, top plate-line electrode layer 246 a and metal-oxidecapacitor dielectric layer 244 a are patterned and etched to removeportions of the bottom electrode layer 242 a, of ferroelectric thin filmlayer 244 a, and of top electrode layer 246 a from non-capacitor areas256 of ILD 230 and from non-memory areas 282, as depicted in FIGS. 3, 8.As a result, a conformal 3-D capacitor laminate 240 covers trench bottom286 and trench sidewall 284 of trenches 234. A conformal capacitorlaminate 240 conforms substantially to the 3-D shape of a trench 234. Aconformal capacitor laminate comprises a bottom electrode 242, a thinfilm 244 of capacitor dielectric, and a top electrode 246, as depictedin FIGS. 8, 8A. In preferred embodiments, a TEOS hardmask having athickness of about 300 nm is deposited on the top surface of topelectrode layer 246 a using a CVD technique known in the art. The TEOShardmask then is patterned using photolithography techniques known inthe art, for example, by depositing a resist, then exposing anddeveloping the resist. A stack etch is then conducted, typically usingRIE, to etch portions of top electrode layer 246 a, ferroelectric thinfilm layer 244 a, and bottom electrode layer 242 a down to ILD 230. Thehardmask then is removed from the top surface of top electrode 246 usingtechniques known in the art, typically RIE. Typically, a resultingcapacitor laminate 240 slightly overlaps a portion 260 of the topsurface of ILD 230.

Generally, in processes 422, a final heating of metal oxideferroelectric thin film 244 in oxygen or nonreactive gas is conductedafter etching processes 420 to achieve desired electronic properties ofpolycrystalline metal oxide. Preferably, a post-TE RTP treatment inaccordance with a low thermal budget MOCVD method of the invention isconducted; for example, at a hold temperature of 725° C. for 2 minutesin O₂ gas. In preferred embodiments, capacitor dielectric 244 comprisingferroelectric layered superlattice material has a thickness in a rangeof about from 25 nm to 300 nm, more preferably in a range of 50 nm to 60nm. Preferably, a thin film of ferroelectric layered superlatticematerial and other elements of a memory capacitor are fabricated using alow-thermal-budget MOCVD technique. Co-owned and co-pending U.S. patentapplication Ser. No. 10/302,441, referenced above, teaches fabricationof thin and ultra-thin films of ferroelectric layered superlatticematerial in nonvolatile memory capacitors.

In processes 424, third ILD 262 is formed on capacitor laminates 240 andon exposed surfaces of ILD 230 of substrate 203 by depositingapproximately 500 nm NSG or doped silicate glass, typically using TEOSor other precursor in a PECVD technique, as known in the art.

In processes 426, an electrically nonconductive hydrogen barrier layer264, as depicted in FIGS. 2, 2A, is formed on substrate 202 bydepositing it on third ILD 262. As discussed with reference to FIGS. 2,2A, and 3, nonconductive hydrogen barrier layer 264 completely coverscapacitors 270. Thus, nonconductive hydrogen barrier layer 264 coversferroelectric thin films 244 of capacitor laminates 240. Nonconductivehydrogen barrier layer 264 further covers switches 208 of integratedcircuit substrate 203 (although it is ordinarily not in direct contactwith switch components such as source/drain regions and gatecomponents). Preferably, nonconductive hydrogen barrier 264 comprisesstrontium tantalum oxide (“strontium tantalate”), having a thickness ofabout 75 nm. Alternatively, nonconductive hydrogen barrier layer 264comprises a laminate structure, which laminate structure comprises asublayer of strontium tantalate, SrTaO_(x), and a sublayer of siliconnitride, SiN. Preferably, strontium tantalate or a SrTaO_(x)/SiNdouble-layer is deposited using a MOCVD process and other techniques andstructures as described in co-owned and co-pending U.S. patentapplication Ser. No. 09/998,469 filed Nov. 29, 2001, which isincorporated by reference. Where barrier layer 264 includes onlySrTaO_(x), a 75 nm thick layer of STO is preferably deposited employingMOCVD. Where barrier layer 264 includes both SrTaO_(x) and SiN, a 75 nmthick sublayer of SrTaO_(x) is preferably deposited first in a MOCVDprocess conducted at between 400° C. and 600° C., employing a SrTa(strontium tantalum) single source precursor. Thereafter, a layer ofSiN, preferably 50 nm to 150 nm thick, is deposited, preferablyemploying CVD. In an alternative embodiment, the SiN portion of barrierlayer 264 may be deposited first, and a layer of SrTaO_(x) is thendeposited on the SiN portion. Liquid spin-on and other liquid-sourcedeposition techniques are also suitable for depositing strontiumtantalate in accordance with the invention. Portions of nonconductivehydrogen barrier layer 264 are generally removed from non-memory areas282 (discussed above with reference to FIG. 3) of substrate 203 inprocesses 426. Typically, resist is deposited and patterned usingphotolithographic techniques, and then an RIE technique is used to etchnonconductive hydrogen barrier layer 264 from non-memory areas 282. Bothstrontium tantalate and silicon nitride, alone or together, function asoxygen barriers, as well as hydrogen barriers.

In steps 428, fourth ILD 268 is formed on hydrogen barrier layer 264 ofsubstrate 203 by depositing approximately 500 nm NSG or doped silicateglass, typically using TEOS or other precursor in a PECVD technique, asknown in the art.

In processes 430, a bit-line contact via 290 is etched through ILD 268,nonconductive hydrogen barrier layer 264, ILD 262, and ILD 230 down todiffusion barrier 227, using techniques known in the art. Similarly, aplate-line contact via 292 down to top plate-line electrode 246 isetched through ILD 268, nonconductive hydrogen barrier layer 264, andILD 262 using techniques known in the art. Preferably, via 290 and via292 are filled with metallized wiring material, typically comprisingcopper, in a single metallization process that forms bit line contact270, bit-line wiring layer 202, plate-line contact 254, and plate-linewiring layer 272. Preferably, plate-line contact 254 or other electricalconnection to top plate-line electrode 246 is disposed remotely fromcapacitors 250, located above each of conductive plugs 222, so that theintegrity of hydrogen barrier layer 264 is preserved directly above andnear capacitors 250. Wiring layers 202, 272 and contact plugs 270, 254are typically deposited by a conventional Al—Cu—Si metallizationsputtering technique.

FIGS. 9, 9A depict mutually orthogonal cross-sectional views of analternative exemplary nonvolatile ferroelectric memory 500 in accordancewith the invention. Integrated circuit memory 500 comprises 3-D memorycapacitors conforming to a pillar shape, instead of a trench.

FIG. 9 shows a cross-section 501 taken along the bit line 502 ofintegrated circuit 500. Integrated circuit 500 includes siliconsemiconductor material 504, field oxide regions 506, and switches 508.Integrated circuit 500 further includes a first insulator layer 518,typically called an interlayer dielectric layer (“ILD”), disposed onsubstrate 503, and covering semiconductor material 504, oxide regions506, and switches 508. First insulator layer 518 typically comprisesnondoped silicate glass (“NSG”) or a doped glass, such as BPSG(boron-doped phospho-silicate glass), and is typically formed using aCVD technique as known in the art. Substrate 503 further includesconductive capacitor plugs 522 and conductive bit-line plug 523. Wafersubstrate 503 may comprise silicon, gallium arsenide, or othersemiconductor, or an insulator, such as silicon dioxide, glass, ormagnesium oxide (MgO).

In accordance with the invention, ILD 518 comprises pillar regions 524on which memory capacitors are disposed. A pillar region 524 is formedby removing non-pillar portions of ILD 518 so that a pillar region 524extends vertically from the non-pillar surface 525 of ILD 518. A pillar524 comprises a pillar top 526 and a pillar sidewall 527. A conductivecapacitor plug 522 is disposed in a pillar region 524 so that the bottomof a conductive capacitor plug 522 is in electrical contact with switch508, and the top of conductive plug 522 forms at least a part of topsurface 526 of pillar 524.

A conductive diffusion barrier 528 is disposed on pillar top 526, pillarsidewall 527, and usually a small overlap portion 519 on non-pillarsurface 525 of ILD 518. Conductive diffusion barrier 528 is inelectrical contact with conductive capacitor plug 522.

Integrated circuit 500 also comprises a bit-line pillar 530, in whichbit-line plug 523 is located. A diffusion barrier 531 is typicallylocated on bit-line pillar 530 and is in electrical contact withbit-line plug 523. Diffusion barriers 528, 531 are made of, for example,titanium nitride, and typically have a thickness of 10 nm to 20 nm.Diffusion barrier layers, such as titanium nitride, inhibit thediffusion of chemical species, particularly oxygen, between theunderlying and overlying layers of memory 500.

In accordance with the invention, a 3-D bottom electrode 534 conformingto the shape of pillar 524 is disposed on diffusion barrier 528. A 3-Dcapacitor dielectric thin film 536 conforming to the shape of pillar 524in accordance with the invention is disposed on bottom electrode 534. A3-D top electrode 538 conforming to the shape of pillar 524 inaccordance with the invention is disposed on dielectric thin film 536.Preferably, capacitor dielectric thin film 536 comprises ferroelectricmaterial, most preferably, layered super lattice material as describedabove. In the embodiment of integrated circuit 500, 3-D top electrode538 functions as a plate-line electrode.

Thus, in accordance with the invention, each pillar 524 is coated with a3-D capacitor laminate 539. A capacitor laminate 539 comprises a bottomelectrode 534, a ferroelectric thin film 536, and a top electrode 538.Pillar 524 is three-dimensional; that is, the shape of pillar 524 hassubstantial vertical components, or directional components substantiallyperpendicular to the horizontal plane of semiconductor substrate 504. Asa result, capacitor laminate 539, which conforms substantially to theshape of pillar 524, also has a 3-dimensional shape. In preferredembodiments, top electrode 538 is a top plate-line electrode thatextends substantially perpendicular to bit line 502 of FIG. 9. Capacitorlaminate 539 on each pillar 524 functions as a ferroelectric memorycapacitor 540 in integrated circuit 500. FIG. 9A depicts a cross-section552 taken along a top plate-line electrode 538 of integrated circuit500. Top plate-line electrode 538 is not planar, rather, it is a plateline in the sense that it extends continuously between a plurality ofmemory capacitors 540 and provides continuous electrical connectionbetween the capacitors and a conductive plate-line connector plug 542.As depicted in FIG. 9, capacitor laminate 539 is not present on anon-capacitor area 544 of top surface 525 of ILD 518 between adjacentcapacitors 540 along bit line 502. Similarly, as depicted in FIG. 9A,bottom electrode 536 is not present on non-memory area 545 betweenadjacent capacitors 540 along top plate-line electrode 538. As depictedin FIGS. 9, 9A, an overlap portion 519 of laminate 539 of the eachcapacitor 540 typically slightly overlaps non-pillar top surface 525 ofILD 530. The footprint, or horizontal surface area, of a capacitor 540is determined essentially by the horizontal area of pillar 524 and thearea of overlap portion 519. The capacitance area of capacitor 540,however, is represented approximately by the surface area of the bottomand sidewall of pillar 524 plus the area of overlap portion 519. Apillar 524 is typically patterned to have a square rectangular shape. Ina square pillar having a height equal to the length of one of its sides,the surface area of its sidewall (all four square sides) is four timesgreater than the surface area of its top. As a result, a capacitor 540in accordance with the invention having a footprint only one-fourth thehorizontal surface area of a conventional horizontally orientedcapacitor of the prior art provides approximately the same capacitancearea. Similar relative proportions are obtained if pillars have circularshapes. A capacitor 540 in accordance with the invention typicallycomprises a bottom electrode having a thickness of about 50 nm, aferroelectric thin film having a thickness of about 50 nm to 60 nm, anda top electrode having a thickness of about 50 nm. Thus, a correspondingcapacitor laminate 539 has a thickness of about 150 nm to 170 nm. Acorresponding cube-shaped pillar 524 in accordance with the inventionhas length, width, and depth dimensions of approximately 350 nm to 400nm, that is, about 0.35 to 0.40 nm. A capacitor 540 in accordance withthe invention typically has a footprint of approximately 0.2 nm². Incontrast, a conventional memory capacitor of the prior art, as depictedin FIG. 1, typically has a footprint of about 0.8 nm² or more.

The bottom and top electrodes of ferroelectric capacitors conventionallycontain platinum. It is preferable that the bottom electrode contains anon-oxidized precious metal such as platinum, palladium, silver, andgold. In addition to the precious metal, metal such as aluminum,aluminum alloy, aluminum silicon, aluminum nickel, nickel alloy, copperalloy, and aluminum copper may be used for electrodes of a ferroelectricmemory. Adhesive layers (not shown), such as titanium, enhance theadhesion of the electrodes to adjacent underlying or overlying layers ofthe circuits.

A second interlayer dielectric layer OLD) 546 made of NSG (nondopedsilicate glass) is disposed on ILD 518 and on capacitor laminates 539. Adoped silicate glass, such as FSG (fluorosilicate glass), PSG(phospho-silicate glass) film, or a BPSG (boron phospho-silicate glass)film could also be used in ILD 546.

Nonconductive hydrogen barrier layer 548 is disposed on ILD 546 to coverthe surface area above ferroelectric thin film 536. Typically, hydrogenbarrier layer 548 is not present over non-memory areas of the integratedcircuit, where there is no ferroelectric thin film 536 needingprotection against reactive hydrogen.

A third interlayer dielectric layer (ILD) 550 made of NSG (nondopedsilicate glass) is disposed on diffusion barrier layer 548. A dopedsilicate glass, such as FSG (fluorosilicate glass), PSG(phospho-silicate glass) film, or a BPSG (boron phospho-silicate glass)film could also be used in layer 550. As depicted in FIG. 9,electrically conductive bit-line connector plug 552 connects bit line502 to switch 508 through electrode material, conductive barrier 529 andbit-line plug 523. As depicted in FIG. 9A, electrically conductiveplate-line connector plug 542 connects wiring layer 556 to topplate-line electrode 538. Wirings 502, 556 preferably comprise Al—Si—Custandard interconnect metal with a thickness of about 200 nm to 300 nm.Typically, a film of adhesion material (not shown), for example,comprising Ti and TiN, is deposited on the substrate, and wiring film502, 556 is then formed on the adhesion film.

FIGS. 10, 10A, 11, and 11A depict intermediate stages in the fabricationof ferroelectric integrated circuit memory 500 of FIGS. 9, 9A. Thediagram of FIG. 12 is a process flow sheet of a method 600 in accordancewith the invention for making a ferroelectric memory 500 in accordancewith the invention. Although method 600 of FIG. 12 is discussed hereinwith reference to FIGS. 9-11A, representing ferroelectric integratedcircuit memory 500 in different of stages of fabrication, it is clearthat the method 600 of FIG. 12 and numerous other embodiments of amethod in accordance with the invention are useful generally forfabricating a 3-D ferroelectric memory capacitor.

In processes 604, a substrate 503 is provided containing siliconsemiconductor material 504, field oxide regions 506, switches 508, andfirst ILD 518 as described above with reference to FIGS. 9, 9A, and asdepicted in FIGS. 10, 10A. In processes 606, first ILD 518 is patternedand etched to form vertical capacitor pillars 524 and vertical bit-lineconnector pillars 530. Capacitor pillars 524 have a pillar top surface526 and pillar sidewall 527.

Typically, patterning of ILD 518 is done in a rectangular or squareshape so that pillars 524 have shapes corresponding substantially tocubes or rectangular solids It is understood, however, that pillars 524may be formed to have virtually any shape, for example, a cylindricalshape. Furthermore, standard etching techniques usually form pillarshaving sidewalls that are not perfectly parallel to the direction ofetching; that is, that are not perfectly perpendicular to the horizontalplane of semiconductor substrate 504. As a result, the top region 526 ofpillars 524 is typically narrower than a corresponding pillar bottom atnon-pillar surface 525 of ILD 518. Nevertheless, a sidewall 527 andcapacitor layers conforming to sidewall 527 have substantial directionalcomponents in the vertical direction, as well as in the horizontalplanes at the overlap area 519 and top 526, and are thereforethree-dimensional.

In processes 608, capacitor pillars 524 and bit-line pillars 530 arepatterned and etched to form vias down to switches 508. in processes610, tungsten plugs are deposited to form capacitor plugs 522 andbit-line connector plugs 523.

In processes 612, a conductive diffusion barrier layer 528 a isdeposited on first ILD 518, including on 3-D pillars 524, 530, asdepicted in FIGS. 10, 10A. In preferred embodiments, electricallyconductive oxygen-diffusion barrier layer 528 a comprises a multilayerstructure comprising an iridium oxide sublayer, which is on an iridiumsublayer, which is on a titanium aluminum nitride sublayer, asrepresented by IrO_(x)/Ir/TiAlN. A preferred barrier stack is fabricatedby first sputtering a sublayer of titanium aluminum nitride having athickness of about 50 nm onto first ILD 518 and conductive plugs 522,523, then sputtering about 100 nm iridium metal onto the nitridesublayer, and then sputtering about 100 nm of iridium oxide onto theiridium sublayer.

In processes 614, a conformal bottom electrode layer 534 a is depositedon 3-D conductive diffusion barrier layer 528 a, as depicted in FIGS.10, 10A. Preferably, conformal bottom electrode layer 534 a has athickness of about 50 nm and comprises platinum. Typically, a bottomelectrode layer is formed by sputtering a platinum target usingtechniques known in the art. Preferably, the electrode is formed by RFsputtering of a platinum single layer, but it also may be formed by DCsputtering, ion beam sputtering, vacuum deposition, or other appropriateconventional deposition process. The bottom and top electrodes of memorycapacitors in accordance with the invention preferably contain platinum.Nevertheless, in certain embodiments, a bottom electrode comprisesanother non-oxidized precious metal, such as palladium, silver, andgold. In addition to the precious metals, a metal such as aluminum,aluminum alloy, aluminum silicon, aluminum nickel, nickel alloy, copperalloy, and aluminum copper may be used to form electrodes of a memorycapacitor in accordance with the invention.

In processes 616, as depicted in FIGS. 11, 11A, portions of bottomelectrode layer 534 a and of conductive diffusion barrier layer 528 aare removed from non-capacitor portions 544 between adjacent electrodesalong the bit-line direction, and from non-capacitor portions 545adjacent to pillars along the plate-line direction, as well as fromnon-memory areas, such as non-memory areas 282 of FIG. 3. In processes616, portions of the bottom electrode layer are removed from ILD 518,but not from the pillars. In preferred embodiments, a TEOS hardmaskhaving a thickness of about 300 nm is deposited on bottom electrodelayer 534 a using a CVD technique known in the art. The TEOS hardmaskthen is patterned using photolithography techniques known in the art,for example, by depositing a resist, then exposing and developing theresist. A stack etch is then conducted, typically using RIE, to etchportions of bottom electrode layer 534 a and diffusion barrier layer 528a, thereby forming diffusion barrier 528 and bottom electrode 534 oneach capacitor pillar 524, and diffusion barrier 529 and electrodematerial 553 on bit-line pillars 530. The hardmask then is removed fromthe top surface of the remaining bottom electrode layer using techniquesknown in the art.

In processes 618, a conformal ferroelectric thin film layer 536 a oflayered superlattice material, or a thin film containing another type ofcapacitor dielectric, is deposited on bottom electrodes 534 and onnon-capacitor areas 544, 545 of ILD 518 in accordance with theinvention, as depicted in FIGS. 9, 9A, using techniques described abovewith reference to method 400. Preferably, ferroelectric thin film layer536 a has a thickness in a range of about from 25 nm to 300 nm,preferably about 50 nm to 60 nm. Particularly useful for forming anultra-thin film of layer superlattice material is a low-thermal-budgetMOCVD method, as described in co-owned and co-pending U.S. patentapplication Ser. No. 10/302,441 filed Nov. 22, 2002, having the title“Low Thermal Budget Fabrication of Ferroelectric Memory Using RTP”,which is incorporated by reference.

In processes 620, a conformal top plate-line electrode layer 538 a isdeposited on ferroelectric layer 536 a, as depicted in FIGS. 7, 7A.Typically, top plate-line electrode layer 538 a is formed by depositingabout 50 nm of platinum using a sputtering technique as known in theart.

In processes 622, portions of top electrode layer 538 a andferroelectric thin film layer 536 a are removed from non-capacitor areasof 544 using patterning and etching techniques known in the art. Inpreferred embodiments, a TEOS hardmask having a thickness of about 300nm is deposited on the top surface of top electrode layer 538 a using aCVD technique known in the art. The TEOS hardmask then is patternedusing photolithography techniques known in the art, for example, bydepositing a resist, then exposing and developing the resist. A stacketch is then conducted, typically using RIE, to etch portions of topelectrode layer 538 a and ferroelectric thin film layer 536 a down toILD 518. The hardmask then is removed from the top surface of topelectrode 538 using techniques known in the art, typically RIE.Typically, a resulting capacitor laminate 539 slightly overlaps aportion 519 of surface 525 of ILD 518. A conformal 3-D capacitorlaminate 539 covers pillar top 526 and pillar sidewall 527 of pillar524. A conformal capacitor laminate 539 conforms substantially to the3-D shape of a pillar 524. A conformal capacitor laminate 539 comprisesa bottom electrode 534, a thin film 536 of capacitor dielectric, and atop electrode 538, as depicted in FIGS. 9, 9A.

Generally, in processes 624, a final heating of metal oxideferroelectric thin film 536 in oxygen or nonreactive gas is conductedafter etching processes 622 to achieve desired electronic properties ofpolycrystalline metal oxide. Preferably, a post-TE RTP treatment inaccordance with a low thermal budget MOCVD method of the invention isconducted.

In processes 626, second ILD 546 is formed on capacitor laminates 539and on exposed surfaces of ILD 518 of substrate 503 by depositingapproximately 500 nm NSG or doped silicate glass, typically using TEOSor other precursor in a PECVD technique, as known in the art.

In processes 628, an electrically nonconductive hydrogen barrier layer548 is formed on substrate 502 by depositing it on second ILD 546, asdepicted in FIGS. 9, 9A. As discussed with reference to FIGS. 9, 9A,nonconductive hydrogen barrier layer 548 completely covers capacitors540. Thus, nonconductive hydrogen barrier layer 548 covers ferroelectricthin films 536 of capacitor laminates 539. Nonconductive hydrogenbarrier layer 548 further covers switches 508 of integrated circuitsubstrate 503 (although it is not in direct contact with switchcomponents such as source/drain regions and gate components).Preferably, nonconductive hydrogen barrier 548 comprises strontiumtantalum oxide (“strontium tantalate”), having a thickness of about 75nm. Alternatively, nonconductive hydrogen barrier layer 548 comprises alaminate structure, which laminate structure comprises a sublayer ofstrontium tantalate, SrTaO_(x), and a sublayer of silicon nitride, SiN.Preferably, strontium tantalate or a SrTaO_(x)/SiN double-layer isdeposited using a MOCVD process and other techniques and structures asdescribed in co-owned and co-pending U.S. patent application Ser. No.09/998,469 filed Nov. 29, 2001, which is incorporated by reference.Where barrier layer 564 includes only SrTaO_(x), a 75 nm thick layer ofSTO is preferably deposited employing MOCVD. Where barrier layer 548includes both SrTaO_(x) and SiN, a 75 nm thick sublayer of SrTaO_(x) ispreferably deposited first in a MOCVD process conducted at between 400°C. and 600° C., employing a SrTa (strontium tantalum) single sourceprecursor. Thereafter, a layer of SiN, preferably 50 nm to 150 nm thick,is deposited, preferably employing CVD. In an alternative embodiment,the SiN portion of barrier layer 548 may be deposited first, and a layerof SrTaO_(x) is then deposited on the SiN portion. Liquid spin-on andother liquid-source deposition techniques are also suitable fordepositing strontium tantalate in accordance with the invention.Portions of nonconductive hydrogen barrier layer 548 are generallyremoved from non-memory areas 282 (discussed above with reference toFIG. 3) of substrate 503 in processes 628. Typically, resist isdeposited and patterned using photolithographic techniques, and then anRIE technique is used to etch nonconductive hydrogen barrier layer 548from non-memory areas. Both strontium tantalate and silicon nitride,alone or together, function as oxygen barriers, as well as hydrogenbarriers.

In processes 630, third ILD 550 is formed on hydrogen barrier layer 548of substrate 503 by depositing approximately 500 nm NSG or dopedsilicate glass, typically using TEOS or other precursor in a PECVDtechnique, as known in the art.

In processes 632, a bit-line contact via is etched through ILD 550,nonconductive hydrogen barrier layer 548, and ILD 546 down to electrodematerial 553 at bit-line pillar 530, using techniques known in the art.Similarly, a plate-line contact via down to top plate-line electrode 538is etched through ILD 550, nonconductive hydrogen barrier layer 548, andILD 546, using techniques known in the art. Preferably, the vias arefilled with metallized wiring material, typically comprising copper, ina single metallization process that forms bit line contact 552, bit-linewiring layer 502, plate-line contact 542, and plat line wiring layer556. Preferably, plate-line contact 542 or other electrical connectionto top plate-line electrode 538 is disposed remotely from capacitors540, located above each of conductive plugs 522, so that the integrityof hydrogen barrier layer 548 is preserved directly above and nearcapacitors 540. Wiring layers 502, 556 and contact plugs 552, 542 aretypically deposited by a conventional Al—Cu—Si metallization sputteringtechnique.

Conformal 3-D ferroelectric thin film layers formed in accordance withthe invention have smooth, continuous, and uniform surfaces, even thoughthey are not planar, and they can be reliably fabricated to havethicknesses in a range of from 25 nm to 300 nm, maintaining importantstructural and electrical characteristics. The reduced heating time atelevated temperature of a low-thermal-budget technique in accordancewith the invention reduces the formation of hillocks and othernon-uniformities at the surfaces of deposited layers. The resultingenhanced smoothness improves interfacial contacts and inhibitselectrical shorting. Conformal ultra-thin MOCVD ferroelectric thin filmsin accordance with the invention preferably are fabricated using amethod as described in co-owned and co-pending U.S. patent applicationSer. No. 10/302,441 filed Nov. 22, 2002, having the title “Low ThermalBudget Fabrication Of Ferroelectric Memory Using RTP”, which isincorporated by reference.

It should be understood that the specific processes and electronicdevices described herein are exemplary; that is, the inventioncontemplates that the layers in FIGS. 2, 3, and 5-11A may be made ofmany other materials than those mentioned above and described below.There are many other variations of structures and methods in accordancewith the invention than can be included in a document such as this, andthe methods and materials may be used in many other electronic devicesother than integrated circuit devices 200 and 500.

A feature of the invention is that the ferroelectric material is made oflayered superlattice materials. A 3-D ferroelectric capacitor is oflittle use unless the ferroelectric material can be made very thin.Otherwise, the footprint of the capacitor will remain very large. It hasbeen found that layered superlattice materials, unlike otherferroelectric materials, can be made extremely thin while stillretaining a high enough polarizability and other electrical propertiesto make an effective memory.

A related feature of the invention is that the capacitor laminate andthe ferroelectric materials are very thin. Now that it has been shownthat layered superlattice materials can be made very thin and retaintheir electrical properties, those skilled in the art may be able to usethe methods of the invention, such as very low thermal budgets, to makeextremely thin films out other ferroelectric materials, and thus makethe memory out of other ferroelectric materials.

There have been described structures and methods for making electronicdevices containing 3-D memory capacitors, in particular, 3-Dferroelectric memory capacitors. It should be understood that theparticular embodiments shown in the drawings and described within thisspecification are for purposes of example and should not be construed tolimit the invention which will be described in the claims below.Further, it is evident that those skilled in the art may now makenumerous uses and modifications of the specific embodiment described,without departing from the inventive concepts. For example, even thougha low thermal budget in accordance with the invention is achieved to asignificant degree through the use of RIP heating, it is conceivablethat furnace-heating could be conducted for a portion of the cumulativeheating time in an embodiment in accordance with the invention. It isalso evident that the steps recited may in some instances be performedin a different order, or equivalent structures and processes may besubstituted for the various structures and processes described; or avariety of different precursors may be used. Consequently, the inventionis to be construed as embracing each and every novel feature and novelcombination of features present in and/or possessed by the fabricationprocesses, electronic devices, and electronic device manufacturingmethods described and by their equivalents.

1-55. (canceled)
 56. A method of forming a ferroelectric memory in anintegrated circuit substrate, comprising: providing an integratedcircuit substrate including a bottom electrode having athree-dimensional (3-D) shape having substantial directional componentsin three mutually orthogonal planes; placing said integrated circuitsubstrate in a chemical vapor deposition chamber, depositing a conformalferroelectric thin film on said bottom electrode using a chemical vapordeposition process; and depositing a conformal top electrode layerconforming to said ferroelectric thin film layer.
 57. A method as inclaim 56 wherein said integrated circuit substrate includes an insulatorlayer, a portion of which insulator layer forms a three-dimensional(“3-D”) insulator surface, and said providing comprises depositing saidbottom electrode layer conforming to said 3-D insulator surface.
 58. Amethod as in claim 57 wherein said integrated circuit substrate includesa switch and said insulator layer is formed above said switch.
 59. Amethod as in claim 56, further comprising processes of removing aportion of said top electrode layer, a portion of said ferroelectricthin film layer, and a portion of said bottom electrode layer to form a3-D capacitor laminate including a top electrode, a ferroelectric filmand a bottom electrode.
 60. A method as in claim 56 wherein saiddepositing a conformal ferroelectric thin film layer comprisesdepositing a ferroelectric thin film layer having a thickness notexceeding 80 nm.
 61. A method as in claim 56 wherein said depositing aconformal ferroelectric thin film layer comprises depositing aferroelectric thin film layer having a thickness not exceeding 60 nm.62. A method as in claim 56 wherein said depositing a conformalferroelectric thin film layer is conducted using a low-thermal-budgetMOCVD technique.
 63. A method as in claim 59 wherein said using a MOCVDtechnique comprises: flowing a metal organic precursor into a MOCVDreaction chamber containing said integrated circuit substrate to form acoating on said conformal bottom electrode layer, said precursorcontaining metal atoms in effective amounts for forming saidferroelectric thin film layer, and heating said substrate including saidcoating using rapid thermal processing at a temperature in a range ofabout from 500° C. to 900° C. for a cumulative heating time notexceeding 30 minutes.
 64. A method as in claim 63, further characterizedin which said cumulative heating time does not exceed five minutes. 65.A method as in claim 63, further characterized by not heating saidsubstrate in a furnace.
 66. A method as in claim 63 wherein said heatingsaid substrate comprises: conducting a pre-TE RTP treatment of saidsubstrate including said coating before said depositing said topelectrode layer, and wherein said heating said substrate furthercomprises conducting a post-TE RTP treatment after said depositing saidtop electrode layer.
 67. A method as in claim 66, further comprisingprocesses of removing a portion of said top electrode layer, a portionof said ferroelectric thin film layer, and a portion of said bottomelectrode layer to form a 3-D capacitor laminate including a topelectrode, a ferroelectric film, and a bottom electrode beforeconducting said post-TE RTP treatment.
 68. A method as in claim 66wherein said conducting said post-TE RTP treatment is done in anonreactive gas.
 69. A method as in claim 56 wherein said depositingcomprises depositing a layered superlattice material.